The present invention relates to an apparatus for spreading a carbon fiber fabric woven from multifilament yarn, that is, an apparatus which, by use of ultrasonic waves, separates carbon filaments from each other that are bonded together with a sizing agent and then spreads the separated filaments.
U.S. Pat. No. 5,016,451 (corresponds to Japanese Examined Patent Publication No. Hei. 4-70420) discloses an apparatus for spreading warps and wefts of a carbon fiber fabric woven with multifilament yarn by applying ultrasonic waves to the fabric in water. As shown in FIG. 3, this conventional apparatus includes a water vessel 2, an ultrasonic oscillator 3 immersed in the water contained in the water vessel 2, a glass guide plate 21 that is opposed to the ultrasonic oscillator 3 in the water, a transfer belt 22 for continuously transferring a carbon fiber fabric 20b along a face 21a of the guide plate 21 which face is opposed to the ultrasonic oscillator 3, and a drying device 23 for drying a carbon fiber fabric 20c that has been output from the belt 22. Feeding speeds of a supply roller 1 and the transfer belt 22 are equalized by an electric circuit incorporated in an electric control box 24, so that no tension is exerted on carbon fiber fabrics 20a and 20b between the roller 1 and the belt 22. This is to protect the carbon fiber fabric, which is likely damaged by a bending force, from strong bending forces as would be applied by a front edge 21b and a rear edge 21c of the guide plate 21 to the carbon fiber fabric when it received tension. Further, a feeding speed of the transfer belt 22 and a rolling speed of a take-up roller 7 that is disposed downstream of the drying device 23 are also controlled by the electric control box 24 so that no tension is exerted on carbon fiber fabrics 20c and 20d that are subjected to drying. In this manner, in the conventional apparatus, no tension is applied to the carbon fiber fabrics 20a-20d from the paying out to the rolling up.
In the above conventional apparatus, since the carbon fiber fabric 20b is transferred while being pressed against the fixed guide plate 21, a frictional force occurring between the fabric 20b and the guide plate 21 may delay a central portion of a weft to thereby curve it. Further, because the carbon fiber fabric 20c should be kept in a non-tension state to prevent it from receiving strong, localized bending forces from the edges of the guide plate 21, the introduction and exit portions of the apparatus adjacent to the guide plate 21 need to be sufficiently long, which necessarily increases the size of the spreading water vessel 2. Further, since the spread fabric 20c is in a non-tension state, surface tension of water may re-bond filaments together (hereinafter referred to as "reintegration"). Still further, a variation in the thickness of right and left selvages and other factors may cause an error in the feeding speed of the selvages, and when accumulated, this error may cause slanted transfer of the carbon fiber fabric 20a.